Hydraulic positioning system for gripping heads of forging machines



May 28, 1963 B. KRALOWETZ 3,091,140 HYDRAULIC POSITIONING SYSTEM FORGRIPPING HEADS OF FORGING MACHINES Filed Dec. 22, 1961 3 Sheets-Sheet lFIG] gu/vg K LWMVV May 28, 1963 B. KRALOWETZ 3,091,140

HYDRAULIC POSITIONING SYSTEM FOR GRIPPING HEADS OF FORGING-MACHINESFiled Dec. 22, 1961 3 Sheets-Sheet 2 nvvn/foi May 28, 1 B. KRALOWETZ3,091,140

HYDRAULIC POSITIONING SYSTEM FOR GRIPPING HEADS OF FORGING MACHINESFiled Dec. 22, 1961 3 Sheets-Sheet 3 STEPPING 43 SWITCH mma/vroz KI UNQ(fix/0445 4 United States Patent 3,091,140 HYDRAULIC POSITIGNING SYSTEMFGR GRIT?- PING TEADS 0F FGRGING MACS Bruno Kralowetz, t. Ulrich, nearSteyr, Austria Filed Dec. 22, 1961, Ser. No. 161,529 Claims priority,application Austria Jan. 7, 1961 6 Claims. (Cl. 78-99) This inventionrelates to an arrangement in forging machines comprising hammer toolswhich are radially movable toward the workpiece and a hydraulicallydisplaceable gripping head for axially feeding the workpiece and havinga hydraulic system which comprises valve means operable by electriclimit switches, which are acted upon by cams which can be set indifferent positions depending on the desired displacement of thegripping head. When the gripping head has been started and a camdepresses the corresponding limit switch, the hydraulic system isswitched over to assume the stop position and the gripping head isstopped. The switching over to effect the displacement of the grippinghead is then also electrically performed, e.g., by means of a steppingswitch. It has now been found that the desired position of the grippinghead determined by the cam which is effective at a time may not bemaintained or may not be reached or may be overrun. This is due to thefact that the gripping head is under the action of longitudinal forceswhich are derived from the forging forces and that it cannot be held inposition by hydraulic means against the action of these forces owing tothe inevitable leakage of oil, the deformation of the conduits and thefact that even a hydraulic fluid is compressible to a slight extent. Thedifficulties involved in stopping and holding the gripping head exactlyin the desired position are due to the fact that feeding is not alwayseffected at the same speed but may be performed at a low speed or a highone, depending on the stroke concerned. The displacement of the grippinghead after the actuation of the limit switch varies with differentspeeds.

It is an object of the invention to provide an improvement in thisrespect by the provision of an arrangement which automatically andimmediately compensates any undesired displacement of the gripping headafter the end of an axial movement so that a more exact result offorging is ensured.

The invention resides essentially in that the cams serving to terminaterespective increments of the displacement of the gripping head haveassociated with them run-up members which have oblique surfaces andwhich can also be set in different positions and each of which isadapted to act on a feeler, which is resiliently urged toward the run-upmember and controls a slide valve, which is additionally provided in thehydraulic system and in response to any undesired movement of thegripping head from the desired position determined by the cam which iseffective at a time causes a hydraulically effected return movement ofthe gripping head to this desired position. The run-up members are setin positions which correspond to those of the cams. With their obliquesurfaces they force the feeler back to a smaller or larger extentagainst the force of the spring acting on it upon each displacement ofthe gripping head so that the additional slide valve is displaced, whichcauses now such a control operation that the desired position isresumed.

In a development of the invention, the hydraulic system comprises anauxiliary slide valve which is operable by the limit switches and whichestablishes the operative connection to the feeler-controlled slidevalve when the system is changed over to the position for stopping thegripping head. It is thus ensured that the feeler-controlled slide valvewill be operative only when the grip- 2 ping head is stopped but doesnot affect the control cycle in other respects.

Forging machines for which the arrangement according to the invention isintended are suitably controlled so that the piston for displacing thegripping head is permanently supplied with the pressure fluid at therod-side end having the smaller effective piston area whereas it issupplied with pressure only from time to time at the cover-side end.This enables a control of the piston movement merely by changing thesupply to the cover-side end. When pressure is supplied to thecover-side end of the piston, the latter will move in spite of thepermanent supply to its rod-side end because the effective piston areaon the cover-side end is much larger. When the cover-side end isconnected to the drain, the piston will move toward the cover becausethe pressure resulting from the permanent supply to the rod-side end islarger. When the cylinder is closed on the cover side, the piston willbe stopped. It is proposed according to the invention to provide in sucha hydraulic system a pressure fluid conduit which leads through theauxiliary slide alve and preferably through a pressureregulating valveto the housing of the feeler-controlled slide valve, on the one hand,and, on the other hand, back through the auxiliary slide valve to thecover-side end of the piston which controls the movement of the grippinghead, the feeler-controlled slide valve being arranged to open or closea discharge conduit depending on the position of the feeler. Since thispressure fluid conduit leads, on the one hand, to the cover side of thegripping head piston and, on the other hand, to the housing of thefeeler-controlled slide valve, there will be equal pressure in thecylinder chamber at the cover-side end of the gripping head piston andin the slide valve housing. When the gripping head is in the desiredposition so that the feeler and its slide valve are in a neutralposition, an equilibrium will be established and the gripping head willnot change its position. On the other hand, if the gripping head isdisplaced from its desired position so that the feeler and with it theslide valve are displaced by means of the oblique surface of the run-upmember, the slide valve will open the discharge conduit toa larger orsmaller extent to reduce or increase the pressure at the cover end ofthe cylinder of the gripping head piston. This will result in acorrecting displacement of the gripping head until the position ofequilibrium of the gripping head is reached.

The feeler-controlled slide valve with the feeler is suitably secured tothe gripping head bed and the gripping head comprises a longitudinalrail for receiving the runup members which can be set in differentpositions. Alternatively, the feeler-controlled slide valve could becarried by the displaceable gripping head and the run-up members couldbe stationary and carried by the gripping-head bed.

An illustrative embodiment of the invention is shown on the accompanyingdrawing, in which FIG. 1 is an elevation showing an arrangementembodying the invention carried by the gripping head bed and thegripping head of a forging machine,

FIGS. 2 and 3 are enlarged sectional views taken on line IIII andIII-III of FIG. 1 and FIG. 4 is a diagram of the electrically controlledhydraulic system for displacing the gripping head.

A forging box 1 accommodates the hammer tools with their drive. A bed 2for horizontally displaceable gripping head 3 is disposed before theforging box 1. The workpiece is gripped by the gripping head and ismoved in longitudinal direction to enter between the hammers. It mayalso be rotated about its axis, if desired. The gripping head 3 isconnected by a rod 4 to a piston 5.

which slides in a cylinder 6, which is accommodated in the gripping headbed 2. These parts as well as the elements for gripping and rotating theworkpiece are known and for this reason are not shown in detail inFIG. 1. On that longitudinal side of the gripping head or gripping headbed which is not visible in FIG. 1, guides for cams 49 which can be setin different positions and limit switches 50 which are arranged to beactuated by the cams are disposed in the manner described hereinbelowwith reference to FIG. 4. Each limit switch controls the flow of currentfrom a source 52 to a valve of the hydraulic system for displacing thegripping head and each cam is set to terminate one of the successivedisplacements of the gripping head by depressing the limit switches sothat the hydraulic system is changed over by the stepping switch 48.

According to the invention, a run-up member 7 having oblique engagingsurfaces 8 is associated with each of these cams. These run-up members 7are secured in a longitudinal bar 9 of the gripping head 3 and can beset in diiferent positions. A feeler 10 is mounted on the gripping bed 2and can be displaced at right angles to the bar 9 and by means of anintermediate lever 11 acts on a slide valve 12. The slide valve 12mounted in a suitable housing 13 is under the action of a compressionspring 14, which urges the slide valve and, through the intermediary ofthe intermediate lever, the feeler against the run-up member 7. Apressure conduit 15 opens into and a drain conduit 16 leads from theslide valve housing 13. Pressure oil enters through a bore 17 an annularspace 18 and through an annular recess 19 in the slide valve 12 reachesanother annular space 20 and through a bore 21 enters the drain conduit16. 22 is a control edge formed by the shoulder of the annular recess19. It is apparent from FIG. 2 that the control edge 22 will more orless open or throttle the discharge of pressure fluid in dependence onthe position of the slide valve determined by the feeler 10'.

FIG. 4 shows the diagram of the entire hydraulic system for displacingthe gripping head. An electric motor 23 drives a pump 24, which sucksthe hydraulic fluid from a reservoir 25 through a filter 26 and forcesit through a check valve 27 into the conduit system. Additional pressureoil handled by a pump not shown may be added from a conduit 28incorporating a check valve if the delivery of the pump 24 is notsuflicient to meet the increased requirement for pressure fluid during ahigh-speed movement. Pressure oil is constantly supplied from a conduit29 through a conduit 30 to the rod-side end of the piston 5. A slidevalve 31 actuated by solenoids 40, 41 and return spring 42, 43 isincorporated in the conduit 29 behind its junction with the conduit 30.A conduit 32 incorporates another slide valve 33 actuated by solenoid 44and a return spring 45 and a conduit 34 to the cover-side end of thepiston 5. 35 is a by-pass conduit incorporating a throttle 36.

A conduit 37 branches from the conduit 31 and passes through anauxiliary slide valve 38 actuated by a solenoid 46 and a return spring47 and a pressure-regulating valve 39. This conduit 37 supplies theconduit 15 to the feelercontrolled slide valve 12 and by a conduit 40which passes back through the auxiliary slide valve 38 is connected tothe conduit 34.

When the slide valve 31 is displaced to the left in FIG.

4 by the solenoid 4t} responsive to closing of the limit switch 50, thepressure oil is free to flow from conduit 29 into conduit 32 or 35.Depending on the position of the slide valve 3-3,'pressure oil entersdirectly the conduit 34 for the high-speed movement of. flows for thelowspeed movement through the conduit 35 and the throttle 36 to thecover-side end of the piston 5. Whereas pressure oil is constantlysupplied to the rod-side end of this piston through the conduit 30, thepiston will now move to the left at low or high speed because the pistonarea on the cover side is much larger than that on the rod side. Whenthe slide valve 31 is displaced by the solenoid 41 to the right from theintermediate position shown in FIG. 4, the conduit 34 will be connectedto the drain either directly through conduit 32 (high-speed movement) orthrough the conduit 35 and the throttle valve 36 (low-speed movement)depending on the energizing of the solenoid 44 by the stepping switch48. In this case the pressure permanently applied to the rod-side end ofthe piston 5 will predominate and the latter will move to the right sothat the gripping head performs a return movement.

As soon as the pressure of the cam 49 which is effective at a time onits associated limit switch 50 deenergizes the solenoids of the slidevalve 31, so that the latter is returned to its intermediate positionshown by the springs 42, 43, the gripping head movement will beterminated because the conduits 34 and 32 or 35 extending from the coverside are closed. At the same time, however, the auxiliary slide valve38' is displaced to the left when its solenoid 46 is energized by thestepping switch 48, and reaches a position, in which the previousblocking of the conduits 37 and 411 is removed. Pressure oil can thenflow from the conduit 31) through conduit 37 to the housing 13 of thefeeler-controlled slide valve through conduit 15 and to the cover-sideend of the piston 5 through conduits 40 and 34. When the gripping headis in the position shown, in which the feeler 1t engages the right-handoblique surface 3 approximately in the middle thereof, the control edge22 will open the discharge conduit 16 just to such an extent that thiscondition is maintained. On the other hand, if the gripping head isunintendedly displaced in one direction or another, whereby the feeler10 and the slide valve 12 are forced inwardly or outwardly so that thedrain conduit is opened or throttled further, the pressure on thecover-side end of the piston 5 will rise or fall and the piston or thegripping head will be displaced so as to return to the original, desiredposition. When a new movement of the gripping head is now performed, theauxiliary slide valve 38 will be moved back to its intermediate positionshown by the spring 47 so that the additional device is renderedineifective until this movement of the gripping head has been terminatedand is followed by another change over, whereafter the next run-upmember initiates the correcting movements. It is obvious that thesame'correcting operations will result when the gripping head does notstop in its desired position and the feeler assumes from the beginninganother than its neutral position.

What I claim is:

l. A hydraulic positioning system which comprises a positioning memberwhich is movable in two mutually op posite, predetermined directions, ahydraulic motor which is operatively connected to said member andadapted to be energized by pressure fluid selectively in either of twomutually opposite senses to move said member in either of saiddirections, a hydraulic circuit for energizing said hydraulic motor,said circuit comprising valve means electrically operable to control theenergization of said motor and the sense in which it is energized, saidsystem further comprising electrically energizable means for operatingsaid valve means, limit switch means for controlling the energization ofsaid electrically operable.

means, a plurality of adjustable cam means, each of which is arranged tooperate said limit switch means in a predetermined position of saidmember, a feeler-controlled slide valve adapted to be connected in saidcircuit, a feeler arranged to control said slide valve by a movement ina first direction, and a plurality of adjustable run-up members, each ofwhich is associated with one of .said cam means and has an obliquesurface, said feeler and run-up members being arranged to be relativelymoved in a second direction, which is transverse to said firstdirection, in response to a movement of said positioning member ineither of said predetermined directions, each of said run-up membersbeing arranged to engage said feeler with a predetermined point of itsoblique surface when said positioning member is in the predeterminedposition in which the cam means associated with the respective runupmember operates said limit switch means, resilient means biasing saidfeeler in said first direction toward said run-up members, said slidevalve being arranged to assume a neutral position when said feeler isengaged by said predetermined point of said oblique surface, saidhydraulic circuit being arranged to energize said motor so as to movesaid positioning member to said predetermined position in response to amovement of said slide valve out of said neutral position when saidslide valve is connected in said circuit.

2. A positioning system as set forth in claim 1, in which saidpositioning member is a gripping head of a forging machine, which isadapted to grip a workpiece and axially move the same.

3 A system as set forth in claim 2, which comprises a bed arranged toguide said gripping head and a longitudinal bar carried by said grippinghead, said feelercontrolled slide valve and feeler being carried by saidbed and said run-up members being carried by said bar.

4. A positioning system as set forth in claim 1, which comprises anauxiliary slide valve arranged to connect said feeler-controlled slidevalve into said circuit in response to the operation of said limitswitch means by one of said cam means.

5. A positioning system as set forth in claim 4, in which said hydraulicmotor comprises a piston having a rod-side end on which the effectivepiston area is relatively small and a cover-side end on which theefifective piston area is relatively large and said valve means arearranged to supply pressure fiuid to said rod-side end constantly and tosupply pressure fluid to said cover-side end from time to time, saidfeeler-controlled slide valve comprising a housing, said hydraulicsystem comprising a pressure conduit incorporating said auxiliary slidevalve and connected between said housing and the coverside end of saidpiston, and a drain conduit controlled by said feeler-controlled slidevalve.

6. A system as set forth in claim 5, in which said pressure conduitincorporates a pressure regulating valve in series with said auxiliaryslide valve.

No references cited.

1. A HYDRAULIC POSITIONING SYSTEM WHICH COMPRISES A POSITIONING MEMBERWHICH IS MOVABLE IN TWO MUTUALLY OPPOSITE, PREDETERMINED DIRECTIONS, AHYDRAULIC MOTOR WHICH IS OPERATIVELY CONNECTED TO SAID MEMBER ANDADAPTED TO BE ENERGIZED BY PRESSURE FLUID SELECTIVELY IN EITHER OF TWOMUTUALLY OPPOSITE SENSES TO MOVE SAID MEMBER IN EITHER OF SAIDDIRECTIONS, A HYDRAULIC CIRCUIT FOR ENERGIZING SAID HYDRAULIC MOTOR,SAID CIRCUIT COMPRISING VALVE MEANS ELECTRICALLY OPERABLE TO CONTROL THEENERGIZATION OF SAID MOTOR AND THE SENSE IN WHICH IT IS ENERGIZED, SAIDSYSTEM FURTHER COMPRISING ELECTRICALLY ENERGIZABLE MEANS FOR OPERATINGSAID VALVE MEANS, LIMIT SWITCH MEANS FOR CONTROLLING THE ENERGIZATION OFSAID ELECTRICALLY OPERABLE MEANS, A PLURALITY OF ADJUSTABLE CAM MEANS,EACH OF WHICH IS ARRANGED TO OPERATE SAID LIMIT SWITCH MEANS IN APREDETERMINED POSITION OF SAID MEMBER, A FEELER-CONTROLLED SLIDE VALVEADAPTED TO BE CONNECTED IN SAID CIRCUIT, A FEELER ARRANGED TO CONTROLSAID SLIDE VALVE BY A MOVEMENT IN A FIRST DIRECTION, AND A PLURALITY OFADJUSTABLE RUN-UP MEMBERS, EACH OF WHICH IS ASSOCIATED WITH ONE OF SAIDCAM MEANS AND HAS AN OBLIQUE SURFACE, SAID FEELER AND RUN-UP MEMBERSBEING ARRANGED TO BE RELATIVELY MOVED IN A SECOND DIRECTION, WHICH ISTRANSVERSE TO SAID FIRST DIRECTION, IN RESPONSE TO A MOVEMENT OF SAIDPOSITIONING MEMBER IN EITHER OF SAID PREDETRMINED DIRECTIONS, EACH OFSAID RUN-UP MEMBERS BEING ARRANGED TO ENGAGE SAID FEELER WITH APREDETERMINED POINT OF ITS OBLIQUE SURFACE WHEN SAID POSITIONING MEMBERIS IN THE PREDETERMINED POSITION IN WHICH THE CAM MEANS ASSOCIATED WITHTHE RESPECTIVE RUNUP MEMBER OPERATES SAID LIMIT SWITCH MEANS, RESILIENTMEANS BIASING SAID FEELER IN SAID FIRST DIRECTION TOWARD SAID RUN-UPMEMBERS, SAID SLIDE VALVE BEING ARRANGED TO ASSUME A NEUTRAL POSITIONWHEN SAID FEELER IS ENGAGED BY SAID PREDETERMINED POINT OF SAID OBLIQUESURFACE, SAID HYDRAULIC CIRCUIT BEING ARRANGED TO ENERGIZE SAID MOTOR SOAS TO MOVE SAID POSITIONING MEMBER TO SAID PREDETERMINED POSITION INRESPONSE TO A MOVEMENT OF SAID SLIDE VALVE OUT OF SAID NEUTRAL POSITIONWHEN SAID SLIDE VALVE IS CONNECTED IN SAID CIRCUIT.